Dewaxing lubricating oils



April 1935. .1. A. ANDERSON 1,998,648

' DEWAXING LUBRICATING 61Ls Filed July 9, 1932 3 Sheets-Sheet 1 ChamberINVENTOR Q, kbmflfirzder on ATTORNEY Dz'lacnt ska/y April 23, 1935. -J.A. ANDERSON DEW AXIN G LUBRICATING guys 5 Sheets-Sheet 2 4 Filed July 9,1932 N KQ ENGN w N 50 INVENTOR Jo/mfiflrzdersorz ATI'ORNE April 1935- J.A. ANDERSON 1,998,648

DEWAXING LUBRICATING OILS Filed July 9, 1952 s Shts-Sheet s Uent \sdr'apvwzg a ma f m I INVENTOR .zlulndaraon ATTORNEY Patented Apr. 23, 1935UNITED STATES PATENT OFFICE DEWAXIN G LUBRIOATIN G OILS tion of IndianaApplication July 9, 1932, Serial N0. 621,692

6 Claims.

This invention relates to the separation of wax from mineral oils andpertains more specifically to a method of crystallizing wax in aparticular manner so that it may be readily separated from oil by coldsettling or by centrifuge.

Most petroleum oils, particularly paraflin and mixed base oils, containsubstantial quantities of paraflin wax which accumulate in lubricatingoil' fractions obtained by distillation. Mid-Continent lubricatingdistillates may contain 10% of paraflin wax; Salt Creek distillates asmuch as wax. For most lubricating purposes, it is necessary to removethis wax so that the oil will not solidify at low temperatures. A verysmall amount of wax will greatly increase the pour point or thetemperature at which the oil congeals. The object of my invention is toremove all of the waxy bodies from lubricating oil which are responsiblefor unduly high pour points.

Heretofore, it has been the custom to dilute oils with naphtha or otherlight hydrocarbons, to chill the diluted oil, to crystallize out the waxand to mechanically separate the wax by filtration, centrifuging orsettling. Filtration is expensive, and is difiicult because of thetendency to clog the filters'and because of the low temperatures atwhich the separation must be effected. Cold settling is the simplestmethod of wax separation, but it is open to the objection that manywaxes will not settle at all and many other waxes will not settlesufliciently to make this process commercially feasible. Paraflin waxcrystallizes in the form of plates or needles which are rather irregularin outline and which interlockor interlace and set up a skeletonframework throughout the entire body of the oil, to all intents andpurposes causing the body of oil to solidify. In mariy oils the amountor nature of the wax is such that that the oil is not solid, but even inthese cases 40 the interlacing of the wax crystals causes entrainment ofso much oil that the oil and wax cannot be readily separated by coldsettling. If such chilled diluted waxy oil is settled in a tank 100,units deep, the 'wax crystals may only settle a few units from the top;if they settle 10 units, it is said that the oil is settled to 90%bottoms. The object of my invention is to provide a method and means forseparating waxy oil byja cold settling process wherein the diluted oiland wax mixture 50 may be settled to about 10% or 15% bottoms. In otherwords, I want to minimize the amount of oil which is entrained by waxand which is either carried down with it or which prevents it fromsettling.

A further object of my invention is to provide a process of dewaxingwhich will require a minimum initial cost, a minimum amount of space anda minmium operating expense, which will at the same time give maximumyield of Wax-free low cold testoil. Other objects will be apparent asthe detailed description of my invention proceeds.

In practicing my invention I utilize certain condensation products tobring about the crystallization of wax in a readily settleable form. Iadd the condensation product before the dewaxing step and make use of itspecifically to cause, the crystallization of wax in a form which can bereadily settled or centrifuged. My theory is that these condensationproducts cause wax to solidify in compact particles instead of inelongated plates or crystals and I reason from this hypothesis thatdiluted oil can be chilled and settled to low bottoms because theinterlacing of wax crystals will be prevented. Microscopic examinationsconfirm this theory and actual tests have demonstrated that diluted oilwhich is 100% solid at 10 F. can be settled to 8% to 15% bottoms bythese condensation products. I have further discovered that the clearsupernatant oil is characterized by a very low pour point, that thesettling rate is much higher than can be otherwise obtained, and thatmarkedly increased yields may be obtained.

My invention will be more clearly understood from the following detaileddescription and from the accompanying drawings which form a part of thisspecification and in which:

Figure 1 represents diagrammatically an elevation of my improved batchsettler.

Figure 2 represents diagrammatically an elevation of my continuoussettler.

Figure 3 represents diagrammatically an elevation of a centrifugesystem, and

Figure 4 illustrates the microscopic appearance of wax crystal structurein the absence of a condensation product;

Figure 5 illustrates the microscopic appearance of wax crystals formedin the presence of a condensation product; and

Figure 6 illustrates the microscopic appearance of another form of waxcrystalstructure in the presence of a condensation product.

My invention will be described in connection with the dewaxing ofMid-Continent treated distillate oil having a viscosity of about '74seconds Saybolt at 210 F. I do not limit myself, however, to anyparticular type of wax-bearing oil,-the invention is applicable'to oilswith viscosities of seconds at 210 F. and seconds at 100 F., alldistillates, untreated as well as treated,

light as well as heavy, Pennsylvania, Coastal, etc. as well asMid-Continent, etc.,any oil containing diflicultly settleable wax.

My condensation products may be described as a resinous material formedby condensation of halogenated hydrocarbons, with aromatic compounds inthe presence of a catalyst such as aluminum chloride, the condensationpreferably being effected in a suitable solvent. Asa halo-. genatedhydrocarbon I-prefer to use chlorinated parafiin wax having a meltingpoint of about 130 F. before chlorination and being chlorinated to about15%. I may use other hydrocarbons, however, such as petrolatum, Montanwax, viscous oils, etc., and I may vary the amount of chlorination overa relatively wide range, although I prefer to use a hydrocarbon withabout 10% to 20% of added chlorine. The aromatic compound is preferablynaphthalene or diphenyl, although other compounds, such as benzene andtoluene, may also be used. I prefer to effect the condensation in thepresence of a chlorinated liquid, such as carbon tetrachloride,chloroform, tetrachlorethane, etc., although other liquid, such asnaphtha, may be 'used if desired. Aluminum chloride or its equivalenthas'been found to be the best catalyst. I

One specific example of my condensation prod-' uct may be made up asfollows:

About 15 parts by weight of aluminum chloride is slowly added withstirring to a solution of parts by weight of chlorinated wax F. meltingpoint with 15% chlorine) and 15 parts of naphthalene in enough carbontetrachloride to maintain all of the ingredients in solution. The

- of naphthalene and 100 parts of chlorinated wax in a' chloroformsolution. Here again the optimum temperature is about 130 to F. Thereaction is usually complete in from one to ten hours.

As above stated, I may use a wide variation of chlorinated orhalogenated waxes or hydrocarbons and I may vary the aromatic compoundand the conditions of condensation throughout a relatively wide range.The expression condensation product as used in the followingspecification and claims is hereby defined to include that class ofsubstances prepared in the manner hereinabove set forth.

Referring to Figure 1, the treated ,(or un- I treated) waxy lubricatingoil distillate is introduced by pipe I0 and mixed with about 0.1% of mycondensation product, which is transferred from storage tank I I throughpipe I 2 by means of pump l3. The waxy oil with the condensation productmixed therewith is introduced by pipe I4 to mixer I5 where it is mixedwith a diluent such as propane from storage tank l6 and pipe I'I, aboutfive parts of propane being added to one part of waxy oil. This mixtureis then selectively introduced by pipes l8 and I9 or 20 into cooling orchill chambers 2| and 22. These chambers may be refrigerated in anysuitable manner by the use of brine coils or by direct expansion ofammonia. I prefer, however, to reing valves 23 and pipes 24 to lowpressure gas main 25. Propane from main 25 is compressed by pump 26,condensed in coils 21, cooled in chamber 28 and finally returned tostorage tank IS.

The diluted oil-wax mixture may be chilled at the rate of about 3 F. perminute. The original mixture may be at a temperature of about 80 to 100F. and the mixture in the chill chambers is reduced to a temperature ofabout 40 F. This cold slurry is then selectively introduced by pipes 29or 30 and 3] or 32 to settling tanks 33 or 34. It should be understoodthat by using a plurality of these tanks one tank may be filled whileanother is being cooled, etc. Further cooling may be effected insettling tanks by removing of propane vapors through reducing valves 35and 36 to low pressure gas line 25. In fact, I may use the settlingtanks to effect the entire chilling by passing the diluted waxy oilmixture directly from mixer l5 through pipes I8, 31, and 3| or 32. Ifadditional propane is required as diluent and/or refrigeration in chillchambers it may be introduced through line 38.

The rapidity with which the wax crystals settle out in settling tanks 33and 34 will depend to a large extent upon the nature of the waxy oil,the

nature of the diluent and the amount and quality of the condensationproduct. If the Mid- Continent stock above described is chilled in theabsence of the pour condensation product, the wax will crystallize inthe form of interlacing needles 39, as shown in Figure 4. By usingcondensation product the wax assumes the form of tiny slightlystar-shaped aggregate 40 or tiny rounded particles 4| (see Figure 4),which settle rapidly and to very low bottoms. In one series ofexperiments, for instance, it was shown that without the use ofcondensation products the wax did not settle at allit gave 100% bottoms;when 0.3% of the condensation product was added, the wax settled to 17%bottoms, and this settling from propane required less than an hour.

The clear oil may be decanted from either settling tank through pipe 42through outlets 43, 44, 45, 46 and 41. Pet cocks (not shown) areprovided adjacent these outlets for sampling the oil before it isdecanted. By having a plurality of these tanks, one of them may besettling while another is being emptied and furthermore, the oil may bedecanted from the upper part of the tank while the wax is settling stillfurther in the lower part. When the clear wax-free oil has beendecanted, I remove the remaining wax slurry from the base of thesettlers through pipes 43 and 44, usually this wax is in the form of aslurry so that it may be readily handled as a liquid, but if .desired Imay melt it by means of steam coils 45 heater coil 50, the finished oilbeing withdrawn.

through pipe 5| and propane being returned to the low pressure gas linethrough pipe 52.

In Figure 2 I have shown a similar embodiment except that instead ofusing a plurality of batch settling tanks I use a large continuoussettler 53 which may be in the form of a hopper bottomed cylinder or alarge horizontal tank. In this case, the wax slurry is continuouslyremoved from the base of the settler by means of screw conveyor 54 andthe clear oil is directly introduced by pipe 55 to the stripper 49. Inall other respects this modification is the same as that described inconnection with Figure 1.

Referring to Figure 3, it will be observed that the slurry from thechill chambers is introduced into the centrifuge 56 instead of into itscold settling tanks. This centrifuge may be of the type commonly used inthe oil industry and may be driven by motor 51. The wax may be deliveredby pipe 58 to collector 59 and it may be transferred therefrom throughpipe 60 by pump 6! to stripping still 62, which is heated by steam coil63, thewax being withdrawn through pipe 64 to suitable storage tank andthe propane being returned through pipe 55 to low pressure gas line. Thediluted wax-free oil is withdrawn from centrifuge through pipe 66 tocollector 61, from which it is pumped through pipe 68 by pump 69 tostripping still 49 as hereinabove described.

When the Mid-Continent distillate was cold settled with four volumes ofpropane without the use of a condensation product and the chilledmixture was allowed to stand for over six hours, the yield of finishedoil was 63% of the weight of the original charge, and the pour point ofthe finished oil was about +3 F.- When the condensation product ofchlorinated paraffin wax and naphthalene was added prior to thesettling, the settling rate was markedly increased, the yield was about10% higher and the pour point of the finished oil was below F.

In another series of tests using filter naphtha as a diluent inthe ratioof three parts waxy oil to seven parts naphtha and using about 0.1 to0.3% of the condensation product referred to above, I obtained 17%bottoms from a diluted oil-wax mixture which was absolutely solid underthe same conditions without the small amount of condensation products.

Generally speaking, the effects of the condensation products inincreasing settling rates and decreasing the bottoms, is more usefulwith larger amounts of diluent and with lighter diluents (higher A. P.I. gravityor lower specific gravity).

The microscopic examination of wax solidified from overhead cuts withand without the use of condensation products supports my theory of howand why I obtain my improved results.

Heretofore this wax crystallized out in the form of interlacing platesor needles throughout the entire mass of the liquid, thereby entrainingthe oil and supporting other wax crystals. It is obvious that in such asystem settling is impossible. The condensation products prevent thistype of crystallization and cause the formation of small aggregates ofneedles or tiny rounded particles which have no tendency to interlockand which may be readily settled or centrifuged.

Instead of using propane as a diluentI may use naphtha, normally gaseouslight hydrocarbon diluents, such as butane, iso-butane, propylene,butylene, etc., antisolvents such as acetone,

methyl formate, nitrobenzene, etc. or mixturesthereof with miscibilityagents, such as benzol and toluol. In other words, the invention is ofgreatest value in light diluents such as propane, but it is not limitedthereto.

The apparatus will, of course, be suitably insulated and provided withvalves, pumps, collector tanks, etc. All of these engineering detailsare commonly known in the art. They form no part of the presentinvention and they will therefore not be described in detail.

The amount of condensation products used may vary considerably. About0.1 to 0.3% of the concentrated resins gives excellent results, but muchlarger quantities can be used if desired.

While I have described my invention in detail and have set forth atheory of operation, it should be understood that I do not limit myselfto either the details nor the theory except as defined by the followingclaims, which,should be construed as broadly as the prior art willpermit.

I claim:

1. The method of separating wax from waxbearing mineral oil whichcomprises adding to said oil a synthetic product formed by the additionof aluminum chloride to a mixture of naphthalene and chlorinated wax,diluting said oil with a diluent, chilling the diluted mixture to effectsolidification of the wax, mechanically removing the wax from thediluted oil, and removing the diluent from the wax-free oil.

2. The method of separating wax from a waxbearing animal oil whichcomprises admixing with a waxy oil and a diluent a small amount of asynthetic product formed by the reaction of naphthalene with chlorinatedwax by the addition of aluminum chloride, chilling the mixture to effectsolidification of the wax in the form of small aggregates, separatingthe solidified wax from the diluted oil, and separating the diluent fromthe wax-free oil.

3. The method of accelerating the rate of settling and increasing thewax-free oil yield of a cold settling process which comprises diluting awax-containing oil with a diluent, adding to said diluted oil a smallamount of a condensation product formed by the reaction of naphthalenewith a chlorinated wax by the addition of aluminum chloride thereto,chilling said diluted oilwax mixture in the presence of saidcondensation product to cause the solidification of wax without theformation of interlacing crystals, and allowing said cold mixture tosettle.

4. The method of claim 1 wherein about .1% to about .3% of the syntheticproduct is added to the wax-bearing oil, based on the weight of thewax-bearing oil.

5. The method of claim 1 wherein the synthetic product is prepared bycondensing the chlorinated wax with the naphthalene, both dissolved in ahalogenated liquid, the aluminum chloride being added to saidingredients.

6. The method of separating wax from a waxbearing mineral oil, whichcomprises diluting said oil with a light diluent for reducing itsviscosity, adding to said oil a small amount of a crystallizationinhibitor formed by reacting a halogenated hydrocarbon with an aromaticcompound by slowly adding aluminum chloride to a molten mixture of saidhalogenated hydrocarbon and aromatic compound at a temperature of about130 to 140 F., cooling the diluted oil containing the crystallizationinhibitor-to effect solidification of the wax in the form of smallaggregates, separating the wax from the diluted oil by utilizing theirdifi'erence in specific gravity, and separating the diluent from thewax-free oil.

JOHN A. ANDERSON.

